Pneumatically controlled operating device for electric circuit breakers



PNEUMATICALLY CONTROLLED OPERATING DEVICE FOR ELECTRIC CIRCUIT BREAKERSFiled Jan. 4, 1952 Sept. 6, 1955 TZ 2,717,288

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I l 'lll II I Il'll l|ll 1 1 Inventor: Milton 1-. Heinbz,

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United States Patent PNEUMATICALLY CONTROLLED OPERATING DEVICE FORELECTRIC CIRCUIT BREAKERS Milton L. Heintz, Philadelphia, Pa., assignorto General Electric Company, a corporation of New York ApplicationJanuary 4, 1952, Serial No. 264,978

Claims. (Cl. 200-97) This invention relates to pneumatically controlledoperating devices for electric circuit breakers and, more par ticularly,to a controlled spring-operated arrangement for imparting openingmovement to electric circuit breakers of the latched-closed biased-opentype.

In circuit breakers of the type wherein relatively movable contacts areseparable within an enclosing arc chute structure so as to draw an arcwhich is extinguished by a blast of fluid pressure, a continuing circuitisolating opera tion may be performed by the simple expedient ofcompletely withdrawing one of the contacts from the arc chute so as toestablish an external isolating air gap. G-f course, it is desirable tohave the arc extinguished before the movable contact is withdrawn toisolative position from the chute. To this end, it is desirable tocontrol the opening speed of the contacts throughout the stroke so as toallow an adequate opportunity for the fluid blast supplied to theinterrupting unit to extinguish the are, for it will be appreciated thatwastage of the fluid is prevented so long as the movable contacteffectively fills the opening in the interrupting chamber through whichsuch contact is movable. Thus an operating device for a circuitinterrupter of this type should, after a fast initial opening movementfor drawing an arc length favorable to extinguishment by the fluidblast, continue to impart a moderated opening movement for a period oftime sufiiciently long for the blast of fluid to effect theextinguishment of the arc and begin scavenging the arc chute of ionizedare products. Thereafter, the fluid blast is shut off while the movablecontact completely withdraws from the interrupting unit to its fullyopen position. Furthermore, in circuit interrupters of the type referredto above, it is desirable to arrest the opening movement of the contactsthereof smoothly and without objectionable rebound from their fully openposition of the associated moving parts.

A principal object of this invention is to provide a pneumatic controlsystem for the opening spring device of a circuit breaker of thefluid-blast type which system effects a controlled opening movement ofthe breaker which in addition is arranged to arrest the opening movementof the parts in a smooth fashion so as to avoid any tendency for theparts to rebound.

In accordance with the invention, a spring-dashpot device having acylinder and piston for controlling the opening movement of the contactsof a circuit interrupter is provided with a by-pass duct communicatingwith opposite ends of the dashpot cylinder and having therein anadjustable valve for regulating the speed of the piston during theinterrupting and isolating opening movement of the circuit breakercontacts. Means including a dumping passage and an undercut portion ofthe piston rod associated with the dashpot piston quickly relieve thepressure built up ahead of the piston at the end of a circuit breakeroperating stroke thereby to prevent undesired rebound of the movingparts.

The invention will be better understood from the following descriptiontaken in conjunction with the accomice panying drawing in which Fig. lis a schematically represented side view of a circuit breaker and itsoperating mechanism in which the principles of the invention areembodied, Fig. 2 is an enlarged cross-sectional view at mid-stroke ofthe opening-spring device and its fluid dashpot control system ascontemplated by the invention, and Fig. 3 is a top view of the samedevice shown in Pig. 2.

With reference to Fig. 1, an interrupter, generally designated by thenumeral 1, is in the closed position and is normally maintained in thecircuit-closed position by the latch-held closing mechanism generallydesignated by the numeral 2, In this arrangement, opening movement ofthe breaker, which occurs upon tripping of the operating mechanism 2, iscontrolled by the spring-dashpot mechanism generally designated by thenumeral 3.

The interrupter arrangement 1 comprises a movable sickle-type contact 4which is pivotally mounted at $3 and which cooperates with a fixedcontact (not shown) which is disposed within the arc chute structure 6.Thus the circuit through the interrupter comprises terminals Li, thefixed contact with chute 6, contact 4 and terminal L2. As is indicatedin the drawing, the pivot 5 for the sickle-type contact 4 is mounted ona conduit 7. Conduit '7 comprises insulating tubular means for supplyinga blast of fluid from a source (not shown) to the arcing passage formedwithin the lower portion of the structure 6. Sickle-type contact 4 isopened when rotated in a cioclo wise direction about the pivot 5 bymeans of the insulating operating rod 3 which is pivotally connected tothe contact 4- at 9. Operating movement of operating rod 8 is controlledby operating crank it which is secured about the square-sectioned shaft11 which is mounted for rotation in a fixed journal support (not shown).The shaft 11 may constitute a jack shaft for simultaneously operatingthree interrupters, such as l, in a triple pole circuit breaker.

For rotating the shaft 11, crank arm 12 is secured thereto which ispivotally coupled at 15 both to the connecting rod 13 from the operatingmechanism 2 and to the crosshead 14 of the openingspring-dashpot device3.

The closing mechanism 2 comprises an output crank 1-5 rotatable about afixed pivot 16a which is driven by a collapsible trip-free thruststructure comprising the links l7, l8 and 19. Crank lie is pivotallyconnected to red 13 at 20 and to the link 17 at Links 17 on whichcomprise the closing tog le are pivotally conn together at the knee 22while the guide link 19 is man for rotation about its fixed pivot 23 andis votally c nnected to the toggle link 18 at pin 24 which also c e alatch roller. The linkage comprising links 17, i3 i9 is maintained inthe closed position shown in the drawings by the non-trippable proplatch 25 which is pivotally mounted at 25a and by the electrically ormanually trippable latch 26 which is pivotally mounted at 26a.

The circuit breaker opens to interrupt its circuit when tripping motionis imparted to the trip latch 2L5 such as by known suitable meansthereby causing rotation of the latch from its holding position in theclockwise direction about its pivot Upon tripping of the latch 26, thetoggle mechanism comprising links 1'7, and 19 collapses toward the leftso that the output crank 16 is then freed to rotate in a clockwisedirection about the pivot 16/: under the bias of spring means forming aninternal part of device 3 acting through crosshead 14 and connecting rod13 thereby imparting counterclockwise rotation to the crank arms "alland i5 accompanied by clockwise or opening rotation of the movablecontact 4.

For the purpose of applying closing power to the operating mechanism, asuitable solenoid element such as is represented by the numeral 27 maybe used. Element 2;! comprises a sole oid having an armature plungerThus upon enei "on of solenoid 2S, plunger 29 is moved upwardly whileengaging a suitable part of the linkage comprising links 17, 13 and 19such as a roller mounted at the pivot 22. At the end of its upwardstroke plunger 29 establishes the linkage upon the prop latch with theseparts and the tripping latch 26 in the positions indicated in thedrawing so as to latch the breaker in the closed position; thedeenergized plunger 29 falling back to its initial position shown. Thedetails of the solenoid operative mechanism such as is shown in thedrawing and designated by the numeral 2 are more fully disclosed inUnited States. Patent 2,458,240 granted January 4, 1949 upon anapplication of R. 3. Baskerville which is assigned to the assignee ofthis invention.

The spring-dashpot device generally designated by the numeral 3, asshown in detail in Pig. 2, comprises a cyl' inder 30 which is pivotallymounted at 31 about a fixed pivot so that it may rock with the angularsweep of the crank 12. Disposed within the cylinder 3% is a piston 32having a piston ring 33 which functions in the usual manner to form aseal between the walls of cylinder 3% and the piston 32. Piston 32 isprovided with a plurality of ports 34 and a non-return valve 35 togetherwith its spring 36 which operates normally to maintain the nonreturnvalve 35 in the position shown so as to close the ports 34. Piston 32 isbiased strongly and upwardly by a pair of compressional contact-openingsprings 37 and 33 whose function is to supply the driving force to thepiston and its associated parts upon tripping of the latch member 26 andcollapse of the latching structure of the operating mechanism 2 asalready explained. The inner spring 33, being the shorter and stronger,may be regarded as the kick-off spring which produces a fast initialcontact separation, while 37 serves as the follow-through spring forensuring a full opening stroke to the contact blade; it being understoodthat the piston 32 is depicted at an instant in mid-stroke on its wayupward when its opening stroke will terminate at the top end of thecylinder 30. Such springs may be augmented by others which mightconveniently be incorporated in the closing operating mechanism 2.

Disposed at the upper end of the cylinder 30 is a closure member 39.Closure member 39 is provided with an aperture 40 through which thepiston rod 41 is slidable. Disposed about the piston rod 4-1 in closefitting relationship is a throat bushing 42 constructed of appropriateanti-friction material and having a radially disposed port opening 43therein. Throat bushing 4-2 is maintained in position by a retainingwasher 44 on which the bushing rests and a gasketed packing plate member45 which is sealed to the closure member 39 by suitable fastening meanssuch as the screws 46. Shifting of the throat bushing 42 is prevented bythe dowel pin 47 which is entered into the hole drilled partially in thethroat bushing and in the closure member 39 as will be obvious from thedrawing. A resilient packing ring 43 which is constructed of rubber orother similar material nests in the recess of the packing plate 45 andeffectively seals the cylinder end about the piston rod 41 so thatinside air is not discharged outside to atmosphere, nor is contaminatedair admitted to the cylinder from without. Closure member 39 is gasketedand secured to cylinder 30 by suitable bolts 49.

For the purpose of regulating the upward opening movement imparted bysprings 37 and 38 to the dashpotting piston 32 when the latched-closedmechanism 2 is tripped, a by-pass passage including the horizontallydisposed passage 50 formed in closure member 39 and the vertical passage51 defined along one side of cylinder 30 establishes communicationbetween the opposite ends of cylinder 30. Flow of fluid through thepassage 50 and 51 can be regulated by the valve means comprising theneedle valve 52 which, as is indicated, is adjustable and which may besecured in any desired position by the locknut 53. Thus, as upwardmotion of the piston 32 progresses, build up of pressure fluid ahead ofthe piston in the upper portion of the cylinder 30 is regulated by theparticular adjustment chosen for the needle valve 52.

Thus by suitable adjustment of the needle valve 52, the acceleratingopening movement of contact 4 will be moderated, after an initial fastcontact-parting movement under the urge of both short and long springs38 and 37 and before appreciable pressure builds up above the piston 32,so that the moderated opening speed gives the fluid supplied through theblast conduit 7 a better opportunity to extinguish the are drawn withinthe arc passage of the chute 6 and, furthermore, such supply of fluidpressure may be cut off and the chute interval pressure diminishedbefore the contact 4 is withdrawn exteriorly from the passage so as toprevent needless waste of the fluid blast.

Normally, the limited relief of pressure fluid due to the action ofneedle valve 52 and by-pass passage 50, 51 would not prevent a certainamount of shock and rebound to the mechanism due to an excess ofpressure being built up as stored energy ahead of piston 32 near the endof its upward travel.

For the purpose of eliminating any such rebound by advantageouslydisposing of this energy, the dumping or transfer passage 54 is providedtogether with a valve constituted by an undercut portion 55 of thepiston rod 41. As will be obvious from Fig. 2, the radially extendingdumping passage 54 registers with the radial port 43 formed within thethroat bushing 42. Thus as the parts approach the end of an openingoperation of the breaker, the undercut portion 55 of the piston rod 41estabiishes communication between the space above the piston 32 withincylinder 30 and the dumping passage 54. Since the dumping passage 54 isin communication with the by-pass passage 51, the accumulated pressureahead of piston 32 is not only quickly relieved but is reappliedusefully to the lower face of the piston to equalize the pressurethereabout so that the follow through spring of the device willpreponderate upwardly, thereby to prevent undesired rebound of, andsmoothly stop, the moving parts. The gasket 56 of resilient materialconveniently serves as the limiting stop which determines the full openposition.

As is shown in the drawing, the cylinder 30 is provided with a drainplug 57 and a fill plug 58 by means of which a suitable level of oil ismaintained in the bottom of the cylinder 30. This constitutes a sump forreceiving and retaining disturbed dust or metallic particles as well asproviding an oil reservoir, the vapor from which is available forlubricating the cylinder walls.

During a closing operation of the breaker by the solenoid device 27,downward motion of the piston rod 41 and of piston 32 charges theopening device 3 by compressing springs 37 and 33. Such motion isachieved without the additional burden of compressing fluid within thelower portion of the cylinder since the disk valve 35 opens against thelight spring 36 so that fluid from below the piston escapes through theports 34 to the region above the piston 32 without generatingobjectionable back pressure.

In thus providing a closed pneumatic dashpot system,

' external dust and grime are excluded such as might impair the reliableoperation of the close-fitting piston in its machined cylinder walls.

While I have shown and described a particular embodiment of theinvention, it will be understood that I do not wish to be limitedthereto and intend in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A'biased-open dashpot device for producing a controlled openingmovement of a latched-closed circuit breaker, said device comprising acylinder containing a compressible working fluid, a piston movableagainst the fluid and having a piston rod adapted to be operablyconnected to the breaker, said piston having a normal charged positionintermediate the ends of said cylinder and being adapted for movementtherefrom toward one end of said cylinder in response to tripping of thebreaker, a closure member mounted at said one end of said cylinder andhaving an opening therein, said piston rod being slidable in saidopening, a bypass passage having its ends in communication with oppositeends of said cylinder, adjustable valve means for restricting the flowof fluid in said bypass passage from said one end of said cylinder tothe other end thereof during said movement of said piston, and a dumpingpassage formed in said closure member and leading from the openingtherein to said bypass passage, said piston rod having an undercutportion for establishing communication between said one end of saidcylinder and said dumping passage as said piston nears the end of itsoperating stroke.

2. A biased-open dashpot device for controlling the opening movement ofa latched-closed circuit breaker, said device comprising a cylindercontaining a compressible working fluid, a piston movable against thefluid and having a piston rod adapted tobe operably connected to thebreaker, said piston having a normal charged position intermediate theends of said cylinder and being adapted for movement therefrom towardone end of. said cylinder in response to opening of the breaker, aclosure member mounted at said one end of said cylinder and having anopening therein, said opening being larger in diameter than said pistonrod, said piston rod being slidable in said opening, means including abushing aflixed in position within said opening and forming asubstantially fluid tight seal with said piston rod, said bushing havinga radially disposed passage therein, a bypass passage having its ends incommunication with opposite ends of said cylinder, adjustable valvemeans in said bypass passage for controlling the flow of fluid from saidone end of said cylinder to the other end thereof during said movementof said piston, a dumping passage formed in said closure member andleading from said radially disposed passage in said bushing to saidbypass passage, said piston rod having an undercut portion forestablishing communication between said one end of said cylinder andsaid dumping passage as said piston nears the end of its operatingstroke.

3. A biased-open dashpot device for controlling the opening movement ofa latched-closed circuit breaker, said device comprising a cylindercontaining a compressible working fluid, a piston movable against thefluid and having a piston rod adapted to be operably connected to thebreaker, said piston having a normal charged pcsition intermediate theends of said cylinder and being adapted for movement therefrom towardone end of said cylinder in response to opening of the breaker, aclosure member mounted at said one end of said cyliner and having anopening therein, said opening being larger in diameter than said pistonrod, said piston rod being slidable in said opening, a bushing affixedin position within said opening and forming a substantially fluid tightseal with said piston rod, said bushing having a radially disposedpassage therein, a bypass passage havin its ends in communication withopposite ends of said cylinder, a dumping passage formed in said closuremember and leading from said radially disposed passage in said bushingto said bypass passage, said piston rod having an undercut portion forestablishing communication between said one end of said cylinder andsaid dumping passage as said piston nears the end of its operatingstroke.

4. In combination, a cylinder containing a compressible working fluidand a piston movable against the fluid and having a piston rod, saidpiston having an initial position intermediate the ends of saidcylinder, an electric circuit breaker operably related with said pistonrod, a latch for holding said breaker in the closed position, means formoving said piston from its initial position to Ward one end of saidcylinder to open the breaker in response to tripping of said latch, aclosure member mounted at said one end of said cylinder, said closuremember having an opening therein through which said piston rod isslidable, a bypass passage having its ends in communication withopposite ends of said cylinder, adjustable valve means in said passagefor controlling the flow of fluid from said one end of said cylinder tothe other end thereof during an operating stroke of said piston, adumping passage leading from the opening in said closure member to saidbypass passage, and an undercut portion formed on said piston rod forestablishing communication between said one end of said cylinder andsaid dumping passage quickly to transfer fluid compressed in said oneend of said cylinder to the other end thereof through said dumping andbypass passages when said piston nears the end of its operating stroke.

5. A dashpot controlled operating device for producing controlledmovement of a member, said device comprising a cylinder containing acompressible working fluid, a piston movable against the fluid andhaving a piston rod adapted to be operatively connected to said member,driving means adapted to be charged so as to be in a condition toactuate said piston, said piston occupying a normal charged positionintermediate the ends of said cylinder when said driving means ischarged, said piston being adapted for movement from said normal chargedposition toward one end of said cylinder in re sponse to discharge ofsaid driving means, a closure mem-- ber mounted at said one end of saidcylinder and having an opening therein, said piston rod being slidablein said opening, a bypass passage having its ends in communication Withopposite ends of said cylinder, adjustable valve means for restrictingthe flow of fluid in said bypass passage from said one end of saidcylinder to the other end thereof during said movement of said piston,and a dumping passage formed in said closure member and leading from theopening therein to said bypass passage, said piston rod having anundercut portion for establishing communication between said one end ofsaid cylinder and said dumping passage as said piston nears the end ofits operating stroke.

References Cited in the file of this patent UNITED STATES PATENTS793,698 Walter July 4, 1905 1,241,533 MacNeill Oct. 2, 1917 1,264,414Mahoney Apr. 30, 1918 1,480,170 Logan Jan. 8, 1924 1,616,540 Morgan Feb.8, 1927 1,768,949 Denison July 1, 1930 2,125,465 Schwager et al. Aug. 2,1938 2,354,889 Smith Aug. 1, 1944 2,451,962 Lindstrom et a1. Oct. 19,1948 FOREIGN PATENTS 112,546 Great Britain Jan. 17, 1918

